1. Field of the Invention
The present invention relates to a water-based ink that is suitable for use in ink jet recording and other methods and can exhibit high gloss on gloss paper and has excellent fixation while maintaining ink reliability such as recovery from clogging, continuous printing stability, and ink storage stability.
2. Background Art
Ink jet recording is a method wherein ink is ejected as droplets through fine nozzle heads to record letters or figures onto the surface of recording media such as paper. Ink jet recording systems which have been developed and put to practical use include a method wherein an electric signal is converted to a mechanical signal using an electrostrictive element to intermittently eject droplets of ink reservoired in a nozzle head section, thereby recording letters or symbols on the surface of a recording medium, and a method wherein ink, reservoired in a nozzle head section, in its portion very close to the ejection portion is rapidly heated to create a bubble and droplets of the ink are intermittently ejected by volume expansion created by the bubble to record letters or symbols on the surface of a recording medium.
Water-based inks comprising a colorant of a dye or a pigment dispersed in water have been proposed as the ink for ink jet recording. In such water-based inks, it is common practice to disperse the colorant in an aqueous dispersant with the aid of a dispersant such as a surfactant or a polymeric dispersant. Various proposals have been made for compositions of such inks. For example, Japanese Patent Laid-Open Nos. 2662/2004 and 75988/2004 propose water-based inks containing a specific vinyl polymer. The claimed advantages of the proposed water-based inks are excellent waterfastenss, lightfastness, rubbing/scratch resistance, and dispersion stability.
Further, Japanese Patent Laid-Open No. 329199/2001 proposes a water-based ink composition for further improving rubbing/scratch resistance. The water-based ink composition comprises polymer particles A comprising a pigment incorporated in a water-insoluble polymer, and polymer particles B.
Printing of the above conventional water-based inks on recording media such as gloss paper, however, sometimes suffer from a problem that, when the resultant recorded matter is placed in or taken out of a clear file and the like, the surface of the recorded matter undergoes a change due to friction with the clear file, or a problem that, when recorded matters are put on top of each other, friction between the surface of the recorded matter and the backside of the recorded matter occurs, leading to a change in surface state.